Electronic circuit tester and method of use

ABSTRACT

An electrical circuit tester including a resistive load and a testing station for detecting the variable load. The testing station includes at least one electrical current transducer capable of detecting the variable load in an adjacent electrical power circuit. The detection of the variable load is communicated to the testing station and a variable load detection function.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending application Ser. No.11/670,089, filed Feb. 1, 2007, which is a continuation-in-part ofapplication Ser. No. 10/997,009, filed Nov. 24, 2004, which issued asU.S. Pat. No. 7,327,274 on Feb. 5, 2008, and which claims the benefit ofprovisional application No. 60/525,004, filed Nov. 25, 2003.

BACKGROUND OF THE INVENTION

The invention is applicable to the field of test equipment forelectrical power circuits.

DESCRIPTION OF THE RELATED ART

Both commercial and residential buildings include electrical circuitsthat power lights, appliances, and consumer electronics. Buildingsgenerally have a common access point such as a circuit breaker panelthat provides a hookup to the power utility tap. Electric power isdistributed throughout the building on or with electrically isolatedcircuits to various rooms in the building. The circuit breaker panelcomprises a plurality of electromechanical switches that connect eachisolated circuit to the power utility tap. Electric power from eachelectrical circuit is accessed at a plurality of plug receptacles orwires connected directly to ballasts.

When a building is constructed, it is common to plan and label thecircuits together with the circuit breakers. Despite that best practicesare to preserve the plan and labeling of the circuits, it is common tolose the plan or the labeling showing which circuits in the building areassociated with which circuit breakers. Loss of the plan or the labelinggenerally makes subsequent changes more difficult and hence more costly.Accordingly, it is desirable to quickly determine which electricalcircuits are associated with which circuit breakers.

Each of the following United States patents or publications presents asolution to the above problem: U.S. Pat. Nos. 3,623,142; 3,982,181;4,121,152; 4,491,785; 4,556,839; 4,642,556; 4,906,938; 5,497,094;5,969,516; 6,054,931; 6,166,532; 6,222,358; and 20060033485. Still, nonedisclose or suggest the following invention.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises an electrical circuit tester which isuseful for determining information about electrical power circuits. Thetester includes at least one load variation device and a testingstation. The testing station includes at least one electrical currenttransducer capable of detecting the load current conditions in anadjacent electrical power circuit. The load current conditions are inputto the testing station and a load variation device detection function,which detects the load conditions on the adjacent electrical powercircuit and particularly, the load conditions imposed by the at leastone load variation device.

Accordingly, it is an object of the invention to provide an electricalcircuit tester including a variable load connected between a livecontact and a neutral contact; at least one electrical currenttransducer having a transducer output, the electrical current transducerfunctionally coupled to the variable load; and a portable testingstation comprising, a variable load detection function in communicationwith the transducer output, and a display device in communication withthe transducer output; whereby, the variable load detection functionidentifies the variable load and displays a representation of theidentified variable load on the display device.

It is a further object of the invention to communicate remotely with aportable display terminal. As such, it is an object to have anelectrical circuit tester, comprising: a load variation device,including a variable load connected between a live contact and a neutralcontact; a portable display terminal; at least one electrical currenttransducer in communication with the variable load and having atransducer output; and a testing station further comprising; atransducer input in communication with a memory device the memory devicein communication with the portable display terminal.

Finally, it is an object of the invention to test an electrical circuitby coupling a variable load to an electrical circuit by coupling thevariable load across the hot and neutral wires of the electricalcircuit; inducing magnetic flux in the electrical circuit by varying thevariable load; functionally coupling a transducer transformer to theelectrical circuit by positioning the transducer transformer in themagnetic flux; sensing the induced magnetic flux; and communicating thesensed magnetic flux to a display device. It is a further object tocommunicate the sensed magnetic field over a wireless link to a portabledisplay terminal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a logical block diagram of an electrical circuittesting station 10 coupled to transducers that are functionally coupled3 to electrical conductors 21 accessible at a circuit access panel 5.Load variation devices 12 are coupled to electrical power circuits 21 atplug receptacles 26.

FIG. 2 a illustrates a first commercially available transducer 13 thatcouples to an electrical conductor 21.

FIG. 2 b illustrates a second commercially available transducer 13 thatcouples to an electrical conductor 21.

FIG. 3 illustrates a circuit access panel 5 having circuit breakers 52and at least two transducers 13 functionally coupled to the conductors21 associated with the circuit breakers 52.

FIG. 4 illustrates a circuit testing station in a protective andportable case 50 for transport, storage and use of the circuit testingstation 10.

FIG. 5 illustrates a logical block diagram of an exemplaryimplementation of the circuit testing station 10. It is preferred thatthe portable display and control terminal 60 and/or the display 204 ofthe testing station each feature touch screen features.

FIG. 6 illustrates an exemplary implementation of a load variationdevice 120.

FIG. 7 illustrates an exemplary implementation of a portable display andcontrol terminal 600 for communicating with, controlling, and/or viewingthe data captured by the circuit tester station 10.

FIG. 8 illustrates a flow diagram for the load variation detectionfunction.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The circuit tester (“tester”) described herein is designed to be used totest or determine useful information regarding a power distributionnetwork. For the purposes herein, a power distribution network comprisesat least two electrically isolated electrical power circuits that derivepower from a common source such as a utility company source. Further,power circuits are ordinarily, but not necessarily, coupled byelectrical conductors 21 (e.g. wire) to a common circuit access panel 5.The circuit access panel 5 provides a common and convenient access pointfor accessing and testing the electric power distribution network. FIG.1 illustrates a logical block diagram of the electrical circuit tester10 and the components of a power distribution network.

FIG. 1 illustrates “N” electrical power circuits as Electrical Circuit₀,Electrical Circuit₁, . . . Electrical Circuit_(N), where “N” is equal tothe total number of electrical power circuits, coupled by conductors 21,to the circuit access panel 5. One or more of the electrical powercircuits may provide electrical power for electrically powered devicessuch as lights, heaters, motors, and ballasts (not illustrated).Further, each of the electrical power circuits in the electric powerdistribution network are accessible via a plurality of access points,such as plug receptacles 26, for accessing and deriving power from theelectrical power circuit to which it is connected.

The standard circuit access panel 5 comprises a physical organization ofa plurality of electro mechanical switches that each provide a junctionbetween each of the electrical power circuits and the utility tapproviding the common source of electric power to the electric powerdistribution network. A typical electro mechanical switch is a circuitbreaker 52 and a typical physical organization of the plurality ofcircuit breakers 52 comprises a stack or column in a panel 5. Eachcircuit breaker 52 is associated with an electrical power circuit, whichis a convenient place to access, couple, or connect to an electricalpower circuit. It is noted however that alternative circuit accesspoints may be more practical depending on the particular situation orinformation desired to be collected by the tester. Using the testerallows the operator to determine useful information about eachelectrical power circuit and learn which receptacles 26 and conductors21 are associated with which circuit breaker 52, and hence whichelectric power circuit.

Still referring to FIG. 1, the electrical circuit tester comprises, acircuit testing station 10 removably and functionally coupled 3 to oneor more of the electrical power circuits. The tester also includes atleast one load variation device 12 that is removably coupled to one ormore of the electrical power circuits. A portable display and controlterminal 60 permits wireless remote access and control of the testingstation 10. Preferred coupling points for the electrical power circuitare a receptacle 26 and a conductor 21 located at or near the circuitaccess panel 5. Particularly, the load variation device 12 preferablycouples to a receptacle 26 and the testing station 10 preferably couplesto a conductor 21 near the panel 5. The load variation device 12includes a connector 126, typically but not necessarily a two orthree-prong plug 126, that is compatible and capable of being coupled tothe receptacle 26 of the electrical power circuit 2. Moreover, it ispreferable to include several load variation devices 12 with the circuittesting station 10 to enable testing or identifying multiple powercircuits in programmable sequence.

The preferred load variation device 12 presents a distinguishable loadcharacteristic on an electrical power circuit 2 that permitsidentification by the testing station 10 of the load variation device12. The preferred distinguishing load characteristic comprises theimposition of a change to the existing steady state power condition ofthe power circuit of significance such that the distinguishable loadcharacteristic of the load variation device 12 is detectible independentof whether or not there are existing constant or variable loads presenton the power circuit. Accordingly, the tester is used without disturbingor having to power-down the devices coupled to and drawing power fromthe circuit.

A preferred distinguishable load characteristic comprises a pulsed loadcondition with pulse waveform characteristics that are known andidentifiable or detectable by the testing station 10. Further, thepulsed load condition is maintained for a time sufficient to permitidentification by the testing station 10. An exemplary pulsed loadcondition comprises a relatively significant power draw or load currentfor a finite period of time. Accordingly, the pulse may have a singleoccurrence and be of a particular duration, or the pulse may occur morethan once, and/or occur on a periodic basis. A preferred value for therelatively significant power consumption is the power associated with aload current of about 0.1 amperes to 10 amperes, however, the preferredload current may be as little as 0.001 amperes and as much as 10,000amperes. Ultimately, the preferred distinguishable load characteristicspecified or used with the tester is that value of imposed load currentthat is capable of being detected by the software and the components ofthe circuit testing station 10. Additionally, if multiple load variationdevices 12 are used, it is preferable to enable that each load variationdevice 12 has a unique load characteristic so that each load variationdevice 12 is distinguishable by the testing station 10 from the otherload variation devices 12. Accordingly, in FIG. 1, each load variationdevice (i.e. Load₀, Load₁, and Load_(N)) is identifiable by the testingstation 10 by its unique and distinguishable load characteristic.

The testing station 10 is preferably housed within a case 50 thatsecures and protects the circuit testing station 10 electronics from theoutside climate. The circuit testing station 10 draws electric power forits electronics by coupling to a source of electric power using astandard plug receptacle 54. Inside the case 50 is a power supply (notshown) that distributes electrical power from the power source coupledto the receptacle 54 to the electrical components within the case 50.The preferred case 50 is structurally organized to promote theportability of the circuit testing station 10. Accordingly, a preferredstructure for the case 50 comprises a “suitcase” style structure 51,comprised of hard plastic halves 52A and 52B, respectively, which areconnected together on one edge by hinges 513, and securably connectablealong on another edge by hardware 514 commonly used to close and securesuitcase halves. A handle 516 and/or wheels (not shown) enable easytransport of the circuit testing station 10. The first half 52A of thestructure 51 includes a plurality of compartments 512 for securelystoring the plurality of load variation devices 12. The second half 52Bof the structure 51 includes the components and electronics facilitatingand implementing the testing capabilities disclosed herein.Particularly, preferred components include a user accessible visualdisplay device 55 that is controllable by the user by buttons or knobs551 to permit changing the displayed data and initiating and operatingthe testing capabilities of the circuit testing station 10. An antennaattachment receptacle 58 facilitates wireless communication with theportable display and control terminal 60. Also included in the secondhalf 52, but ordinarily concealed to the user are the electronics thatimplement the capabilities of the circuit testing station 10.Accordingly, the placement of the electronic components in the drawingis for explanatory purposes.

The circuit testing station 10 couples to at least one electricalcurrent transducer 13 that is capable of being functionally coupled 3,or that is functionally coupleable 3, to a conductor 21 associated withelectrical power circuit. The electrical current transducer 13preferably functionally couples 3 to the conductor 21 near or at thecircuit access panel 5. In FIG. 1, functional coupling 3 of thetransducer 13 and a conductor 21 is represented by complementary up anddown arrows (i.e. “↑↓”). The transducer 13 includes a transducer output142, which couples, using a transducer conductor 132, to at least onetransducer input 141 associated with the circuit testing station 10. Forthe purposes of this description the transducer 13 functionally couples3 to a conductor 21 by detecting or sensing the current in the conductor21. Moreover, unless otherwise expressed, the transducer 13 mayfunctionally couple 3 to the conductor 21 associated with the electricpower circuit using any technique that permits the detection of thecurrent flowing in the conductor 21. It follows that the transducer 13may couple magnetically, electrically, or by detecting a radiation, suchas heat or infrared energy, to a conductor 21 associated with anelectric power circuit 2. Finally, it is preferable that the transducer13 detect the changes in load current in the electrical power circuitconductor 21 induced by a load variation device 12 as described herein.

A first type of a transducer 13 that functionally couples 3 to anelectrical power circuit conductor 21 uses magnetic field couplingbetween the transducer 13 and the conductor 21. A preferred transducer13 according to this embodiment includes a transducer transformer 131and a transducer conductor 132. Magnetic field coupling the transducertransformer 131 to the conductor 21 comprises locating the transducertransformer 131 in the magnetic field generated by, or associated with,the electrical power circuit conductor 21. FIGS. 2 a-2 b illustratetransducers 13 including a transformer 131 particularly well suited formagnetic field coupling as described herein. The transducers 13 comprisea hinged 134 split or solid core transformer loop that can be opened(not shown) and closed around a conductor 21. As illustrated, thetransformer 131 encircles, or is located around, the electrical powercircuit conductor 21. Further, the illustration shows the transducer 13coupled relatively close to the circuit breaker 52. The position of thetransformer 131 in relation to the conductor 21 generates induceddetectable current in the transducer conductor 132 that isrepresentative of the current in the conductor 21. It is preferred thatthe transducer 13 produce output current in the transducer conductor 132current that is proportional to the detected current flowing in theconductor 21 associated with the electrical power circuit.

FIG. 3 illustrates positioning of transducers 13 at or near the accesspanel 5. The preferred manner of locating the transducer 13 in themagnetic field generated by, or associated with, the electrical powercircuit conductor 21 comprises encircling or locating the transformer ofthe transducer 13 around the cross sectional perimeter of the electricalpower circuit conductor 21. The side face plate of the circuit accesspanel 5 is removed to expose the conductors 21 associated with thedistinct electrical power circuit conductors 21 for each electricalpower circuits. Locating the transducer 13 around the electrical powercircuit conductor 21 comprises locating the transducer transformer 131of the transducer 13 in the magnetic field generated by the currentflowing in the electrical power circuit conductor 21. Exposure to themagnetic field as described causes functional coupling 3 of thetransducer 13 and the electrical power circuit.

Functional coupling 3 of the transducer 13 and the electrical powercircuit causes induced electric current to flow in the transducerconductor 132 coupled to the transducer transformer 131. The inducedelectric current is ultimately output to components in the circuittesting station 10. Moreover, a separate transducer 13 can be used witheach electrical power circuit and associated conductor 21 to enable themultiple induced electric currents associated with the several loadvariation devices 12 to be detected. Yet another embodiment of atransducer 13 (not shown) uses an infrared sensor to detect radiationassociated with the current flowing in the electrical power circuitconductor 21. The infrared transducer 13 includes an infrared lens thatdetects temperature changes associated with the varying load conditioninduced by a load variation device 12.

The transducer 13 detects the electrical current flowing in theelectrical power circuit conductor 21 to which it is coupled andgenerates a known linear output that is representative of the currentflowing in the conductor 21 to which it is coupled. Moreover, it ispreferred that each transducer output 142 comprise a differential outputsignal that is coupled or coupleable to a transducer input 141 of thetesting station 10. It follows that the preferred means to couple thetransducer 13 to the input(s) is a conductor 132 having pairedcomplementary conductors to minimize amount of common mode noisedetected and displayed in the scaled representation of the load currentin the power circuit. Further, the testing station 10 has severaltransducer inputs 141, represented as: {input_(n=0,1,2,N-1); where N isthe number of circuits to be tested}, which permits that a plurality oftransducers 13 and load variation devices 12 can be concurrently usedwith the testing station 10.

It is preferred that each of the transducer input circuits 141 includean analog to digital converter that converts the analog transduceroutput 142 into a digital representation (i.e. circuits_(N) [0:N]),which is mapped to at least one memory 22 location. Storage of the loadcurrent data input in memory 22 permits the testing station 10 todisplay or graph the historic or real time transient load condition ofeach power circuit. Storage of the load current data input into memory22 also enables the programmable controller 20 to perform mathematicaloperations on the sensed load condition. More particularly, by comparingthe sensed load conditions on an electric circuit to specific amplitudeand transient conditions representing each load variation device 12, thetesting station 10 may detect each load variation device 12 and indicatewith which electrical conductor 21 it is associated.

Within the testing station 10, a data representation of each powercircuit current, represented as “Circuits_(N) [0:N]” in FIG. 1, iscoupled to a load variation detection function 16, which is representedas a load variation detection circuit or load variation detectionprogram since it is appreciated that the load variation detectionfunction 16 can be implemented using electronic devices or by electronicdevices controlled by a software program, or in a combination thereof.Accordingly, the load variation detection function implementation issubject to a design choice provided that the implementation enables thetesting station 10 to detect and distinguish each load variation device12. Preferred designs of the load variation detection function 16 willinclude a filtering function which can be implemented in a variety ofmanners including software or hardware filters, or edge detectioncircuits. The filtering function permits the circuit testing station 10to distinguish between the plurality of load variation devices 12 andother loads present on a electrical power circuit 2.

In a software or hardware filter implementation of the load variationdetection function 16, the filter design passes and/or amplifies aparticular frequency, or a range of particular frequencies, associatedwith the pulses that a particular load variation device 12 applies to aelectrical power circuit 2. The filter also attenuates and/ordiscriminate against frequencies or periods other than the particularfrequency or period of load variation detection device 12 pulsesdesired. In this implementation, a plurality of software or hardwarefilters are designed, and each software or hardware filter is designedto pass the distinguishing load variation frequency or period of oneload variation detection device 12 and attenuate the other loadvariation frequency or period.

In an edge detection implementation, the load variation detectionfunction detects load pulse durations and load pulse edge transitions. Acharacteristic load condition associated with one load variation device12 comprises at least one initial transitional edge and a subsequenttransition edge. Further, it is preferred, but not necessary, that thesubsequent transition edge will be the opposite polarity of the initialtransition edge. Further, it is expected that at least anothersubsequent transitional edge will occur at a predetermined time intervalknown to the testing station 10.

One implementing the load variation detection function 16 is to includea load pulse threshold detector and a pulse duration counter. The loadpulse threshold detector includes a pulse amplitude detector thatqualifies or measures the amplitude and the polarity of each pulse ofload current in the conductor 21. If the pulse amplitude, as measured bythe initial transition edge, is of the proper polarity and of sufficientor correct magnitude, the pulse duration counter is started. If the loadcurrent pulse is of sufficient duration (i.e. not the result of a noisespike on the conductor 21), the pulse duration counter is stopped orreset when the subsequent transition edge of the load pulse is detected.Additionally, the pulse duration counter may measure the time lapsebetween load pulses to determine the period of the load current pulses.Accordingly, if a load current pulse of appropriate magnitude, polarityand duration is detected, the testing station 10 may store the result,alert the user, trigger an alarm, and/or transmit the load current pulsedetection to the portable display and control terminal 60. Accordingly,by programming the amplitude, the polarity, and the duration of eachload pulse for each load variation device 12 into the tester station 10,a user can identify each of the plurality distinct load pulsecharacteristics associated with each load variation device 12.

The load variation detection function 16 is coupled to memory 22 and adisplay device 24 which displays a visual representation of the currentflowing in the electrical power circuit 2 to which the load variationdevice 12 is coupled. By viewing the display device 55, the operator ofthe tester described herein can observer whether a particular receptacle26 is associated with a electrical circuit breaker 52, which is alsoassociated with a particular electrical circuit. Further, because theload variation detection function 16 is designed or programmed toidentify the plurality of load variation devices 12, the operator mayobserve and distinguish between each load variation device 12.

FIG. 8 illustrates a flow chart of an implementation of the process foridentifying and distinguishing the load characteristic(s) associatedwith a load variation device 12 (Load_(N)). After a start 202 of theprogram, which will include a boot up of the operating system on theprogrammable controller 20, the load variation detection softwareprogram is loaded into memory and run by the operating system of theprogrammable controller 20. The software program begins collecting andstoring data 208 for the electrical circuits_(N) for display 210 and/orfuture reference in mathematical operations. The software program alsomonitors the load current in circuit_(N), and upon the detection of aload current transitional edge of correct polarity, starts a load pulseduration counter 220. If the load current pulse is maintained for asufficient duration 230, the software program identifies the circuit towhich the load variation device 12 is connected 240. Further, althoughnot shown in the flow diagram, the software program can continue tomonitor to see if a subsequent edge transitions also match theconditions of the same Load_(N), which would identify periodic loadcurrent pulse trains. The software program also transmits the identifiedcircuit_(N) and a Load_(N) 250 to the portable control and displayterminal 60. Finally, if all the circuits_(N) are identified and matchedwith Load_(N) 260, the software program terminates or waits for furthercommand. Alternatively, if all the circuits_(N) are not identified ormatched with a Load_(N) 260, the software program loops 270 looking fordistinguishing load current characteristics associated with a Load_(N).

Exemplary Implementation

It is noted that the following describes an exemplary implementation ofthe circuit tester components and that a person of ordinary skill in theart could modify or adapt the teachings herein to implement the aspectsof the invention differently in either hardware, software or acombination thereof. Further, the description of commercially availablecomponents or the features of said components should not lead one ofordinary skill in the art to conclude that the design is limited to thefeatures or limits of the disclosed components.

Certain capabilities of the testing station 10 are implemented using amicrocontroller to enhance the capabilities and facilitate the design ofthe testing station 10. FIG. 5 illustrates a logical block diagram ofthe exemplary implementation. The testing station 10 includes at leastone analog input circuit 140 that is coupleable to the transduceroutputs 142, and also coupled to a programmable logic controller (PLC),a microcontroller, or a microprocessor (hereafter “programmablecontroller 20”) which is operating or running a load variation detectionprogram 16. In the implementation, an OpenNet™ controller from IDECIZUMI Corporation was used as the programmable controller 20. Theprogrammable controller 20 is coupled to (or is integrated with) atleast one memory device 22, and a display 24 having user input 26capabilities to control the operation of the programmable controller 20and the testing station 10.

The analog input circuit(s) 140 of FIG. 5 comprises a plurality ofindependent analog input circuits 140 implemented on independent channelanalog input cards 56 (see FIG. 4) which are connectable and communicatewith the programmable controller 20 over a data bus 201. In theimplementation, the programmable controller 20 couples to a 6-channelAnalog Input Module (Part No. FC3A-AD1261) that inputs standard four totwenty milliamp direct current (4 to 20 mA DC) current. Each transduceroutput 142 is coupled to one input of each analog input card 56.

Each analog input circuit 140 includes an analog to digital converterthat translates the 4 to 20 mA DC signal from the transducer output 142into a digital representation of the analog current sensed at thetransducer 13 input. The digital representation of the analog currentvalue is written to a memory location associated with the transducerinput 141. Moreover, in the exemplary implementation, four milliampsoutput from the transducer output 142 is converted to zero units in adigital representation, and twenty milliamps (20 mA) output is convertedinto four thousand (4000) units in a digital representation. FIG. 2illustrates the representation of each analog electrical currentrepresentation as circuits_(N) [0:N].

The transducers 13 are functionally coupled 3, with magnetic fieldcoupling, to electrical conductors 21 at the panel 5. Particularly, thetransducers 13 are coupled around the electrical conductors. Transduceroutputs 142 are coupled to the analog input circuits 140 and detect thedistinguishable load characteristic associated with the at least oneload variation device 12 according to the load variation and detectionprogram running on the programmable controller 20.

The transducers 13 of the exemplary implementation comprise splitmagnetic field coupling transducers. Particularly, transducers 13acceptable for use available as commercial embodiments and include, butare not limited to, the AC Current Transmitters from Absolute ProcessInstruments, Inc. having part numbers CTX-ACR-0, CTX-ACR-1, CTX-ACR-2and CTX-ACR-3S, CTX-ACR-4S. The transducers 13 measure or sense true RMSAC in an associated conductor 21 up to 200 Amps AC and output standardfour to twenty milliamp (4-20 mA) Direct Current. In the exemplaryimplementation, the transducer 13 is coupled to the electrical conductor21 by encircling the transducer 13 the conductor 12. Power for thetransducer is provided by the analog transducer inputs 141 of thetesting station 10.

A block diagram of an exemplary load variation device 12 is illustratedin FIG. 6. The load variation device 12 comprises a load variationcircuit 120 including at least one alterable load element that isconnectable to an access point in a power circuit. An exemplary loadvariation circuit 120 comprises a time delay relay 125 connectable inseries with power resisters (“R”) 122 that are selected and connectablewith a three position switch 123 in alternate combinations to create thealternate load element connected to the power circuit by a plug 126. Forexample, in the illustration, with the three position switch 123 in theposition shown, three (3) power resisters 122 will be connected acrossthe hot and neutral wires of the power circuit. Similarly, the threeposition switch 123 also has positions that will connect both one (1)and two (2) power resisters 122 if desired. The time delay relay 125 ispositioned in the load variation circuit 120 in series to enable theload condition to be connected to the power circuit for a time specifiedby the time delay relay 125. Accordingly, the load conditions connectedto the power circuit may be altered both in magnitude, by adjusting thethree position switch 123, and/or in duration, by setting the time delayrelay 125 to pulse on and/or off (i.e. permit current flow) for aspecified duration.

A portable display and control terminal 600 permits remote control andreceipt of information captured by the tester 10. FIG. 7 illustrates alogical block diagram of the portable control and display terminal 60.The terminal 600 also incorporates a programmable controller 620 that isconfigured and programmed to allow remote control of the testing station10 and review of the data displayed and/or captured by the testingstation 10. The controller 620 communicates 623 via RS232 ports with atouch screen display device 602 and a radio transceiver 630 equippedwith an antenna 635. Power to the terminal 600 is supplied either viabattery 640 or via DC power created by a AD/DC converter 630 that ispowered by and coupled to available electrical power by a plug.

Although the invention(s) have been described in detail with referenceto one or more particular preferred embodiments, persons possessingordinary skill in the art to which this invention pertains willappreciate that various modifications and enhancements may be madewithout departing from the spirit and scope of the claims that follow.

The invention claimed is:
 1. A method of detecting a single occurrenceof a pulse of load current in a plurality of electrical circuits,comprising: coupling a plurality of transducer transformers to aplurality of electrical conductors comprising the plurality ofelectrical circuits; sensing the magnetic flux in each of the pluralityof electrical circuits; reading first digital representations of thesensed magnetic flux in each of the plurality of electrical circuits;inducing additional magnetic flux in at least one of the electricalcircuits by coupling a single occurrence pulse of load current to one ofthe plurality of electrical circuits; reading second digitalrepresentations of the sensed magnetic flux in each of the plurality ofelectrical circuits; detecting a change from the first digitalrepresentations to the second digital representations induced by thesingle occurrence pulse of load current; and identifying on which of theplurality of electrical conductors the single occurrence pulse of loadcurrent was coupled.
 2. The method of detecting in claim 1, wherein; thesingle occurrence of pulse of load current is between about 0.1 and 10amps and lasts for between 10 milliseconds and 10 seconds.
 3. The methodof detecting in claim 2, wherein; the single occurrence of pulse of loadcurrent is about 2 amps and lasts for about 3 seconds.
 4. The method ofdetecting in claim 1, further comprising; communicating the identity, onwhich of the plurality of electrical conductors the single occurrencepulse of load current was coupled, to a display device.
 5. The method ofdetecting in claim 1, further comprising; setting a plurality ofreference points equivalent to each of the first digital representationsof the sensed magnetic flux in each of the plurality of electricalcircuits.
 6. The method of detecting in claim 1, wherein; coupling aplurality of transducer transformers to a plurality of electricalconductors coupling comprises closing split-core transducers around theplurality of electrical conductors.
 7. The method of detecting in claim1, wherein reading first digital representations further comprises;converting, by an analog to digital converter, the sensed magnetic fluxin each of the plurality of electrical circuits to digitalrepresentations that are stored in at least one memory location.
 8. Themethod of detecting in claim 1, wherein detecting a change from thefirst digital representations to the second digital representationsinduced by the single occurrence pulse of load current furthercomprises; comparing the first digital representations to the seconddigital representations.
 9. The method of detecting in claim 1, whereininducing additional magnetic flux in at least one of the electricalcircuits by coupling a single occurrence pulse of load current,comprises; coupling a resistive load across at least one of the hotwires in one of the plurality of electrical circuits.
 10. The method ofdetecting in claim 9 wherein, coupling a resistive load across at leastone of the hot wires in one of the plurality of electrical circuits,comprises; coupling a resistive load across the hot and neutral wires ofone of the plurality of electrical circuits.
 11. The method of detectingin claim 1, wherein coupling a plurality of transducer transformers to aplurality of electrical conductors comprises; placing each of theplurality of transducer transformers in magnetic flu flux of theplurality of electrical conductors.